Exactly right, Lord of the Rings would have made it's money in the Cinema circuits worldwide over and over again, so when they get to putting it out on DVD thats icing on the cake, production costs are negligible for transferring it onto DVD.
As a Cameraman and film editor I can tell you, copyright for the music alone used in Catching the Impossible would have been about £3000 to £4000, with an additional fee for the quantity of disc's produced, there is copyright free music available for sale but by comparison it's rubbish, it's not cheap making films, there's all sorts of costs that push it up
I have just watched the first two episodes on the disc, and it is absolute first class, not only the quality of the picture, but the quality of the subject and the editing is superb, and the underwater scenes are something else, for pricing, you can only compare it to what else is on the market in that category, I think it is good value for the money